A 338 ARC suppressor needs a .338-caliber or larger bore rating, and the right design depends on the firearm and the ammunition. For a bolt action, use an enclosed suppressor. For a semi-automatic AR15 with subsonic ammunition, use an enclosed suppressor; with supersonic ammunition, a flow-through suppressor is recommended. Chattahoochee Munitions manufactures 338 ARC firearms for suppressed shooting: the CM7S bolt action in 8, 12.5 and 16 inches and the CM15 AR15 in 8.5, 10.5 and 16 inches, every barrel threaded 5/8×24.
Which 338 ARC Suppressor for Which Firearm?
| Firearm | Ammunition | Recommended suppressor |
|---|---|---|
| CM7S bolt action | Subsonic | Enclosed |
| CM7S bolt action | Supersonic | Enclosed |
| CM15 semi-automatic | Subsonic | Enclosed |
| CM15 semi-automatic | Supersonic | Flow-through |
This is a recommendation, not a compatibility limit. Any suppressor rated for .338 caliber or larger and threaded to fit will mount.
Why a Bolt Action Gets an Enclosed Suppressor
The CM7S is manually operated. There is no gas system and no cycling bolt carrier, so a bolt action adds no action noise and no gas at the ejection port. Back pressure has nothing to disturb. An enclosed suppressor contains the gas fully within its baffles, which suits a firearm where the muzzle is the only source of sound.
338 ARC Suppressor Choice on an AR15
A semi-automatic uses gas to cycle, and a suppressor raises the pressure in that system. With subsonic ammunition the gas volume is modest, so an enclosed suppressor works well, and the CM15’s Superlative Arms adjustable gas block and Odin Works adjustable buffer let you tune it. With supersonic ammunition the gas volume rises, and a flow-through suppressor is recommended to limit the back pressure that sends gas toward the shooter’s face and speeds up the action.
Subsonic Ammunition Removes the Crack
A suppressor reduces muzzle blast. It cannot remove the sonic crack a supersonic bullet makes along its flight path. The 307 gr Sub-X, rated by Hornady at 1,050 fps, stays below the speed of sound, so a suppressed subsonic 338 ARC has no crack. That pairing is the reason the cartridge exists. See 338 ARC subsonic.
Bore Size and Caliber Rating
A 338 ARC suppressor must be rated for .338 caliber or larger. A .30-caliber suppressor is too small for a .338-inch bullet. A larger-bore suppressor also lets one can serve several cartridges. The PLACID 375 is an enclosed suppressor rated from 5.56 NATO through .375, so it covers 338 ARC, 8.6 Blackout, 300 Blackout and 375 Raptor.
Mounting
Mounting a 338 ARC suppressor starts at the muzzle threads. Every Chattahoochee Munitions 338 ARC barrel is 416R stainless, finished in E100 Blackout Cerakote, with 5/8×24 muzzle threads and a shouldered crown. CM7S barrels come from Mos-Tek. The CM15 ships with an optional muzzle brake selection or a thread protector, so you can mount a direct-thread suppressor or a mount system of your choice.
Barrel Length With a Suppressor
A 338 ARC suppressor adds length, which is why short barrels suit 338 ARC. In Chattahoochee Munitions testing, 338 ARC powder use is largely complete around 12 inches, so a 10.5-inch CM15 or a 12.5-inch CM7S with a suppressor stays compact without giving up much subsonic velocity. Shorter barrels leave more pressure at the muzzle, which the suppressor has to absorb. See 338 ARC barrel length.
Hearing Protection
A 338 ARC suppressor makes the shot much quieter than an unsuppressed one, but the result is not hearing safe. NIOSH sets the recommended exposure limits for impulse noise, and suppressed gunfire can still exceed them. Wear hearing protection.
Legal Notes
Suppressors are regulated under the National Firearms Act in the United States, and state laws vary. Check federal, state and local law before you buy or use a suppressor.
338 ARC Firearms for Suppressed Shooting
- CM7S 338 ARC 12.5-inch bolt action pistol or SBR
- CM7S 338 ARC 8-inch bolt action pistol or SBR
- CM7S 338 ARC 16-inch bolt action rifle
- CM15 338 ARC 10.5-inch AR15 pistol or SBR
- CM15 338 ARC 8.5-inch AR15 pistol or SBR
Compare platforms in 338 ARC bolt action vs semi auto and see every configuration in Containment Zone 338.
338 ARC Suppressor FAQ
What suppressor do I need for 338 ARC?
One rated for .338 caliber or larger. Use an enclosed suppressor on a bolt action and on an AR15 with subsonic ammunition; a flow-through suppressor is recommended on an AR15 with supersonic ammunition.
Can I use a 30-caliber suppressor on 338 ARC?
No. A .30-caliber bore is too small for a .338-inch bullet.
Is suppressed 338 ARC hearing safe?
No. It is much quieter than unsuppressed, but still loud enough to require hearing protection.
What thread pitch is a 338 ARC barrel?
Every Chattahoochee Munitions 338 ARC barrel is threaded 5/8×24.
Does 338 ARC need a flow-through suppressor?
Only on a semi-automatic with supersonic ammunition is a flow-through suppressor recommended. A bolt action, or an AR15 with subsonic ammunition, takes an enclosed suppressor.
Can one suppressor cover 338 ARC and 375 Raptor?
Yes, if it is rated for .375 caliber. The PLACID 375 is rated from 5.56 NATO through .375.
Why does subsonic ammunition matter with a 338 ARC suppressor?
A suppressor reduces muzzle blast but cannot remove the sonic crack of a supersonic bullet. Subsonic ammunition removes the crack.
Who makes a 338 ARC rifle for suppressor use?
Chattahoochee Munitions manufactures the CM7S bolt action and the CM15 AR15 in 338 ARC with threaded 416R barrels from 8 to 16 inches, and twist rates matched to the 307 gr subsonic bullet.